As a type of a double-gate transistor that has a structure in which one or more gate electrodes sandwich the channel region so that the gate electrodes can more positively control current flowing thereunder, there is a fin field effect transistor (FinFET) which is a transistor with a fin structure. In a FinFET, it is important to make its fin thinner since a channel with a fully-depleted structure needs to be formed therein.
However, FinFETs with conventional structures has the following problem. Specifically, since each of such conventional FinFETs has a thin fin, the entire body of the fin is unintentionally silicided while a silicide layer is formed on surfaces of the fin. This increases parasitic resistance in the FinFET. It is difficult to silicide just the vicinity of the surfaces of a thin fin, and even if just the vicinity of the surfaces of a thin fin should be successfully silicided, agglomeration may possibly occur in the thus-formed thin silicide layer during a thermal process of manufacturing processes of the transistor.
Accordingly, techniques to solve the above problem have been heretofore provided. In these techniques, crystals of silicon or the like are epitaxially grown on surfaces of a fin made of silicon, and thereafter a silicide layer is formed on the upper surface of the thus-formed epitaxial-crystal layer, thereby preventing the body of the fin from being entirely silicided. (For example, refer to Japanese Patent Application Publication No. 2005-86024).
Meanwhile, there has been known a type of a FinFET including multiple fins that are arranged in parallel in order to obtain larger gate width and thereby to obtain sufficient current. (For example, refer to Japanese Patent Application Publication No. 2002-9289)
However, in such a FinFET including multiple fins, the multiple fins will naturally require a larger layout area on the substrate of the FinFET. Accordingly, in the case where epitaxial crystals are formed on surfaces of the fins so that the bodies of the fins can be prevented from being entirely silicided, the size of each epitaxial crystal may possibly increased to be in contact with other devices adjacent thereto. This will cause short circuit between the devices.